1. Field of the Invention
The present invention relates in general to the field of fuel cells and thermal exchange devices, alternatively known as heat sinks and, more particularly, to a fluid-permeable heat sink that is integrated with a byproduct of the fuel cell to cool a component or components thermally coupled to the heat sink.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
It is generally known that fuel cell technology provides a source of electric power. Fuel cells are electrochemical devices that convert the chemical energy of a reaction into electrical energy. The basic physical structure or building block of a fuel cell consists of an electrolyte layer in contact with a porous anode and cathode on either side of the electrolyte.
In a typical fuel cell, gaseous fuels are fed continuously to the anode and an oxidant, such as oxygen from air, is fed continuously to the cathode. The electrochemical reaction takes place at the electrodes to produce an electric current caused by ion conduction flow between the anode and cathode.
Although having components and characteristics similar to those of a typical battery, a fuel cell differs in several respects. A battery is an energy storage device and will cease to produce electrical energy when the battery is discharged. A fuel cell, on the other hand, is an energy conversion device that has the capability to produce electrical energy for as long as the fuel and oxidant are supplied to the electrodes.
The ion conduction flow results from the fuel and oxidant gases flowing past the surfaces of the anode or cathode, opposite the electrolyte at the other surface of the anode and cathode. The fuel, oftentimes hydrogen, reacts with the oxidant to form a water byproduct. Hydrogen, however, is not the only type of fuel used in fuel cells. Any fuel that can be burned galvanically at the anode and any oxidant that can be reduced at a sufficient rate encompasses all the various types of fuels and oxidants used in fuel cells. Gaseous hydrogen and oxygen has become the fuel of choice for most applications since it is readily available and economical. Moreover, use of hydrogen and oxygen gases produce a byproduct of water. Water is both stable and easily disposed.
The efficiency of a fuel cell is dictated primarily by the amount of electrolyte between the electrodes, and the porosity of the electrodes. If the electrolyte becomes to plentiful, the electrode (even though it is usually very porous) may “flood” and restrict the transport of the gaseous species and the transfer of the ions across the electrolyte. In an effort to control the problems of flooding, the fuel cells are typically monitored and the temperature of operation is carefully controlled. For example, the electrolytes can either be solid or aqueous. If aqueous electrolytes are used, the temperatures must be limited to approximately 200° C. or lower in order to achieve a proper vapor pressure and to reduce degradation that would occur if vapor were to exist as a byproduct transport medium. To minimize flooding, temperatures of the fuel cell are oftentimes lowered using various coolant devices.
As set forth in U.S. Pat. No. 4,826,741 (herein incorporated by reference), cell flooding and electrolyte membrane dehydration can be reduced if direct air cooling or liquid cooling is applied to the fuel cell itself. For example, a thermal exchange device, such as a heat sink, can be thermally attached to the fuel cell. Air is forced to flow across the fins of the heat sink to cool the fuel cell and prevent the water byproduct of a hydrogen-fed fuel cell from flooding at the electrode surfaces.
Details of thermal exchange devices, such as a heat sink, are readily available in the industry. For example, U.S. Pat. No. 6,841,250 describes one form of heat sink, with fins extending a spaced distance from each other through which air is forced to travel. The surfaces of a typical heat sink are solid and non-porous. Once the air strikes the non-porous surface, the thermally conductive, solid surface (typically thermally conductive metal) is cooled, and the cooling effect is transferred throughout the heat sink attached to the fuel cell.
While utilizing a heat sink to cool a fuel cell beneficially improves the performance of the fuel cell, the improvement is nonetheless limited to fuel cell operation. It would be desirable to implement the benefits of cooling a fuel cell while also cooling yet another heat source altogether different from a fuel cell. It would be further beneficial to utilize the byproduct of a fuel cell as the cooling medium of a heat source, regardless of whether the heat source is a fuel cell, electronic component, or both. By deriving an improved mechanism of having a porous heat sink evaporatively cool a heat sink, water therein not only provides a benefit beyond the conventional art, but also does so in a convenient manner in which cooling takes place with an already existing water supply.